<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>

        function abc() {
            console.info(this)
        }
        abc();

        function Person(){
            debugger
            console.info(this)
        }

        Person(); // this === window
        var p1 = new Person(); // this === Person的对象

        console.info(null == undefined); // true
        console.info(null === undefined); // false
        console.info(NaN === NaN); // NaN false
    </script>
    <a href="test2.html">test2</a>
</head>
<body>
    
</body>
</html>